Answers

I plant mine in the autumn and dont expect much the first spring but after that they do well. These like partial shade and I sometimes divide them after flowering usually in March they are very pretty. Generally snowdrops do better the first year when planted in the green so you may find pots of them in your garden centre about now?

Yes they are always better planted 'in the green', so as Drc said the pots on sale in GC's are a good way of getting them. Of course if you already have some then what Drc said, when flowering is over divide them and replant.

In the green which means before they have died back NOT in the autumn. If you want you need to order now for delivery in next 2 or 3 months and plant immediately. Bulbs that have ben allowed to dry out will now grow well.

Undoubtedly the GC will have pots in - probably forced... unlikely to flower well the following year. No 'in the green' means that the grower digs them up immediately they finish flowering and send out for planting then and there. We've actually done it for a friend's daughter who was desperate for snowdrops in her garden and had failed miserably with dried bulbs.
As a thought you couldn't plant anything in the ground right now here and as the snow goes back the snowdrops are already very visible.

I have planted them as dry bulbs in the autumn, and 'in the green' in the spring. The latter have always given me the best results. Come early spring, on the back pages of BBC Gardeners World Magazine, the advert pages, there are always snowdrops advertized for mail ordering. They will come held in bunches with elastic bands in a bulging, muddy jiffy bag (and a very muddy invoice note, handled by the wet, muddy grower ... I can just picture the poor person in the rain). Plant them straight away or as soon as you can when you receive them. Like Moon grower says, they will have been very freshly dug up.